Build a garden pond
Follow our step by step guide to building a garden pond.

Materials

sand
pond liner
pond pump
aquatic plants

Tools

spade
hosepipe

Choosing the site

First you must decide where to site your pond. Have it close to the house if you want to it to be visible for most of the year. Choose a level site if possible and avoid placing your pond at the foot of a hill where water might run underneath the pond liner and lift it. Ponds at the foot of slopes may also be subject to fertiliser run-off which will cause algal blooms.

If you want to grow aquatic plants, you should try to place the pond in a site that will get around 5 to 6 hours sunlight per day and you should also avoid placing your pond under trees where it may get clogged up with fallen leaves.

Deciding the shape and depth

What shape you want your pond to be is really a matter of personal taste. A more freeform style such as a kidney shape is suitable for wildlife ponds and informal gardens whereas a square or rectangle lends your pond a contemporary feel.
To help you decide on a suitable shape, you can use a garden hose to mark out the shape before you begin to dig.

The depth of your pond will be determined by whether or not you want to keep fish. Depending on the type of fish you want to keep, make sure you know the minimum recommended depth. For aquatic plants, the bare minimum is 50cm.

You will also need to construct shelves within the pond for growing marginal plants and to provide an escape route for any wildlife that might accidentally fall in. Then, depending on the type of edging you want to use around the pond, you will need to dig out a shelf or sloping sides to hold the edging.

It is a good idea to draw a cross-section of your pond to determine where you will have the deepest parts and where you will position the shelves - just as in the example below.

Digging out the pond and preparing for the liner

Next comes the hard part. Digging out and preparing the pond is likely to take some time and you should try to do this as early in the day as possible and, in particular, on a dry day. What you don't want to happen is that you dig out the pond one day and it rains overnight before you can place the liner or you will be baling out a muddy puddle the next morning.

First, dig out the shape of the pond as well as you can. Then, you need to check the levels all round so that when you fill with water, you don't leave pond liner showing. The banks of the pond should be as level as possible from one side to the other in all directions. Spend some time getting this right as it is something that is very difficult to correct at a later stage.

When you are happy with the shape, depth and levels, you then need to go over every bit of the bottom and sides and check for stones, branches and sharp objects that might pierce the liner. This is another important step that you should take your time over.

Next, you need to provide a bed for the liner. You can use soft sand for this. Slightly moist sand works best and you simply pack the sand, to at least 10cm deep all over the bottom and the sides. You can use a plasterer's trowel for this. You can also use an old piece of carpet or you can buy pond underlay. Either way you need to make sure you provide a good, soft bed for the liner to prevent any stones, etc. you might have missed from piercing it.

Laying the liner and filling the pond

Now its time to lay the liner. The best type of liner to use is a heavy duty butyl liner. Liner thicknesses vary as does the price but you should aim to buy the best you can afford. To calculate the amount of pond liner required measure the width of the pond at its widest point, the depth at its deepest and the length at its longest. Then use the following formula:
For the width: Width plus 2 x depth plus 30cm
For the length: Length plus 2 x depth plus 30cm
So for a pond that is 1m wide, 50cm deep and 2m deep, you would need a pond liner that is 2.3m wide by 3.3m long.

Carefully lay your liner across the pond and let it fall naturally into the space. It won't fall all the way to the bottom but you don't need to force it. As you fill the pond, the liner will fall and begin to take up the shape of the pond. Use bricks or broken slabs to prevent the edges of the liner from falling into the pond.

Start filling the pond. This will take some time depending on the size of your pond but you need to be around while the pond is filling up since you will have to carefully fold the liner into the sides and the bottom to avoid showing creases in the finished pond. You will also need to move the bricks you have used to weight down the liner to allow it to fall. Keep on filling and folding until you are happy with the result.

Finishing

When the pond is completely full, you are ready to finish it with a suitable edging material. For suggestions of pond edging, see our article Edging ponds

Before you plant or add fish, you need to let the water sit for around a week or, if you're in a hurry, you can add a de chlorinator before planting.